Pelvis Radiograph

This webpage presents the anatomical structures found on pelvis radiograph.

pelvis radiograph

Radiographs or X-rays are one of the many diagnostic imaging modalities used to diagnose and evaluate pelvic disorders.

In particular, X-rays are a basic tool for studying the hip and are always used in initial examinations of hip and pelvic issues(1).

Anatomy of the Pelvis

The pelvis is a ring of bones situated between the spine and the legs. The pelvis is composed of three bones(2):

  • The sacrum, a triangular bone at the bottom of the spinal column
  • The coccyx, also referred to as the tailbone
  • The hip bones, also known as the pelvic girdle, comprise three fused bones: the ilium, ischium, and pubis

X-ray Views of the Pelvis

Although there are several different X-ray views to evaluate the hip and pelvis region, the anteroposterior pelvic view (AP pelvic view) is used in standard studies. X-ray studies help physicians determine the displacement of the bones(3).

The AP pelvic view is useful in evaluating the acetabulum (hollow part of the hip’s ball-and-socket joints) and the joint space while in a standing position(4).

Using the AP pelvic view alone results in a correct diagnosis in 94% of fracture cases(5). Fractures discovered in the AP pelvic view may be evaluated further using special X-ray views, such as the inlet and outlet view or oblique view.

In some assessments, it is crucial to use the AP pelvic view to avoid false positives resulting from hip rotation or flexion (bending).

Evaluating and Interpreting Pelvic X-rays

In interpreting pelvic X-rays, the first variable to check is quality control. Quality control pertains to the pelvis’s symmetry, tilt, and rotation in the image(6).

It is essential to check the alignment or symmetry of the following(7):

  • Femoral heads or the tops of the femur bones
  • Obturator foramina or the large opening created by the ischium and pubis where blood vessels pass
  • Ischial spines, which are small, conical projections on the ilium(8)
  • Greater and lesser trochanters, which are protuberances on the upper part of the femur and serve as attachment points for muscles(9)

X-ray analyses also evaluate the surrounding soft tissues(10). Normal soft tissues should be rectilinear (straight lines) and well-defined.

Soft tissues that are convex or curve outward may be a sign of distension (stretching) due to a hip joint filled with fluid(11).

The ABCS approach helps medical professionals conduct a systematized approach when interpreting an X-ray(12):

  • “A” for adequacy and alignment - ensuring that the entire pelvis is visible and the pelvis parts are aligned
  • “B” for bones - examining the outer edges of the pelvic bone for fractures, starting from the pubic symphysis (cartilaginous joints in the pubic bones) and continuing to the left or right side
  • “C” for cartilage and joints - inspecting for signs of widening or overlapping of bones in the sacroiliac joints (joint between the sacrum and iliac bones) and pubic symphysis
  • “S” for soft tissues - checking the soft tissue shadowing in the inner and outer sides of the pelvis for hematoma or tissue edema (swelling)

Types of Pelvic Ring Injuries

Abnormal findings in the pelvis are likely due to injuries and fractures. There are four types of pelvic ring disruptions or injuries, according to the Young-Burgess system(13):

  • Anterior posterior compression is characterized by an opening or separation of the pubic bone by at least 2.5 cm.
  • Lateral compression encompasses a variety of fractures and central hip dislocations.
  • Vertical shear may cause complete ligamentous injury, such as torn ligaments or pelvic ring fractures.
  • Complex pattern is characterized by a combination of any three types of pelvic ring injuries.

Pelvic Fractures

Pelvic fractures are potentially life-threatening issues. A study showed that the overall mortality rate from pelvic fractures was 10%(14). People of advanced age (65 years and up) have an over threefold higher risk (18.6%) than younger individuals (5.7%).

Patients who recovered from pelvic fractures may still have a lower quality of life and a higher risk of medical complications, such as chronic pain, impaired mobility, and sexual dysfunction(15).

Pelvic fractures are classified as either stable or unstable(16).

Stable fractures occur when there is only one break in the pelvic ring. In this type of pelvic fracture, the broken ends of the pelvic bones line up properly(17).

In contrast, unstable fractures occur when there are at least two breaks in the pelvic ring and the broken bones are displaced (not aligned correctly). Unstable fractures often occur due to high-energy events(18).

Examples of high-energy events are motor vehicle accidents and falls from a significant height, such as a ladder.

Although computed tomography scans offer greater insight into the joint anatomy and bone lesions than X-rays, plain radiography is still a fundamental imaging modality for diagnosing hip and pelvic disorders.

References

  1. Chiamil, S. M., & Abarca, C. A. (2016). Imaging of the hip: a systematic approach to the young adult hip. Muscles, ligaments and tendons journal, 6(3), 265–280. https://doi.org/10.11138/mltj/2016.6.3.265
  2. Dunbar, R. P. & Lowe, J. A. (2016, February). Pelvic Fractures. American Academy of Orthopaedic Surgeons. Retrieved from https://orthoinfo.aaos.org/en/diseases—conditions/pelvic-fractures/
  3. Ibid.
  4. Chiamil, S. M., & Abarca, C. A. (2016). Op. cit.
  5. Nikolic, S. & Prosen, G. (n.d.). How to read pelvic x-rays. International Emergency Medicine Education Project. Retrieved from https://iem-student.org/how-to-read-pelvic-x-rays/
  6. Chiamil, S. M., & Abarca, C. A. (2016). Op. cit.
  7. Ibid.
  8. Crumbie, L. (2020, Nov. 13). Bony pelvis. Kenhub. Retrieved from https://www.kenhub.com/en/library/anatomy/the-pelvis
  9. Trochanter. Merriam-Webster.com Dictionary, Merriam-Webster. Retrieved from https://www.merriam-webster.com/dictionary/trochanter. Accessed 24 Jan. 2021.
  10. Chiamil, S. M., & Abarca, C. A. (2016). Op. cit.
  11. Ibid.
  12. Nikolic, S. & Prosen, G. (n.d.). Op. cit.
  13. Alton, T. B., & Gee, A. O. (2014). Classifications in brief: young and burgess classification of pelvic ring injuries. Clinical orthopaedics and related research, 472(8), 2338–2342. https://doi.org/10.1007/s11999-014-3693-8
  14. Keil, D. S., Gross, S., Seymour, R. B., Sims, S., & Karunakar, M. A. (2018). Mortality After High-Energy Pelvic Fractures in Patients of Age 65 Years or Older. Journal of orthopaedic trauma, 32(3), 124–128. https://doi.org/10.1097/BOT.0000000000001041
  15. Dunbar, R. P. & Lowe, J. A. (2016, February). Op. cit.
  16. Ibid.
  17. Ibid
  18. Ibid.

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